It is often necessary for a physician to sample the cellular contents of a patient's lung to determine the nature of an observed abnormality. Cell samples from lesions on the periphery of the lung may sometimes be obtained by direct lung puncture, wherein a needle is driven through the chest wall. This technique is not only painful, but also may result in lung collapse. Lesions near the center of the lung require more invasive diagnostic procedures, such as the conventional thoractomy, a surgical incision of the chest wall. Thoractomies are dangerous and can only be considered for use with patients healthy enough to survive the trauma of major surgery.
In Wang et al., "Bronchoscopic Needle Aspiration Biopsy of Paratracheal Tumors", Volume 118, American Review of Respiratory Disease, 1978, a transtracheal needle aspiration technique is described, wherein a stiff esophageal varices needle is inserted into the lung through the lumen of a rigid bronchoscope. This is a relatively noninvasive technique, but it has substantial limitations. There is a great deal of patient discomfort associated with rigid bronchoscopy, and it is often not possible to manuever the rigid bronchoscope for access to the more distal regions of the lung.
Biopsies have also been made with a flexible fiber optic bronchoscope, conventionally used to visually inspect the lungs. Such bronchoscopes include a small diameter flexible viewing tube, which allows the physician to enter the airways of the lungs through the larynx. The tube is usually advanced through the nose and down the windpipe, with a minimum of discomfort to the patient. Conventionally, tissue is sampled by means of a small spoon-shaped forceps which is passed through a hollow aspirating channel in the viewing tube. The small size and opening range of the forceps limit the amount of tissue that can be retrieved, with a resulting reduction in capability of obtaining adequate specimens for cytologic examination. Also, forceps are unable to reach mass lesions under the lining of the airways, or lesions far out on the edge of the lung. Further, the biting and ripping action of the jaws of the forceps is not conductive to obtaining clean specimens with minimal chance of bleeding.